This application is a national stage of PCT International Application No. PCT/EP2005/012616, filed Nov. 25, 2005, which claims priority under 35 U.S.C. §119 to German Patent Application No. 10 2004 058 831.7 filed Dec. 6, 2004, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a subframe for a utility vehicle.
Utility vehicles which are provided for transporting predominantly heavy loads include, among other things, a chassis frame on which a superstructure for the transportation of the loads is arranged. Furthermore, these chassis frames also serve to receive appliances which are specially to be transported, such as, for example, a mixing drum in the case of a concrete mixer, or a container.
As a rule, the superstructures and subframes provided for them are not provided by the actual manufacturer of the utility vehicle but rather are subsequently fitted individually on the chassis frame of the utility vehicle, depending on the intended use of the vehicle. For this purpose, corresponding connecting mechanisms must be provided between the subframe and the chassis frames.
The basic structure of a subframe essentially comprises two longitudinal members on the chassis frame on both sides of the utility vehicle, which longitudinal members run parallel to each other in the longitudinal direction of the vehicle and are connected via a plurality of crossmembers. To increase the stability, diagonal crosses can be provided, if appropriate in some sections, between the longitudinal members, such diagonal crosses comprising two intersecting oblique struts. At a plurality of points, the subframe has connecting brackets via which it is fastened to the chassis frame. As a rule, the individual support structures are designed as square or rectangular hollow supports made of steel.
A subframe of the generic type, such as disclosed for example in German utility model DE 298 00 368 U1, is connected to the main frame of the chassis exclusively by means of screws. For this purpose, diverse intermediate add-on parts and intermediate angles and also flanges have to be provided in order to form corresponding connecting surfaces between the longitudinal members and crossmembers.
A frame structure which is likewise screwed to the chassis frame is known from German laid-open specification DE 196 25 380 A1. This subframe is to serve as a base for a superstructure for, for example, a box, a tank or a loading platform, and is connected to the chassis via diverse securing elements on the longitudinal members of the subframe. In this connection, grids of holes in the form of a matrix are provided on the securing elements to a sufficient extent such that positioning in different positions in relation to the chassis is possible in order to compensate for dimensional measurements in chassis frames of different manufacturers.
In subframes of this type, it is generally desirable to obtain savings of weight, where possible, and nevertheless to ensure adequate stability in order to support the load to be transported by the utility vehicle. Furthermore, weld seams are to be avoided in subframe structures of this type, since they lead (with the loads to be supported) to considerable stress concentrations which, in the most unfavorable cases, lead to failure.
One object of the present invention is to provide a subframe of the type described above, which achieves a further saving of weight with at least constant or improved stability.
Another object of the invention is to achieve a more favorable dissipation of the forces originating from the load to be supported without substantial deformations within the individual components of the subframe with welding work being avoided in the subframe.
These and other objects and advantages are achieved by the subframe for a utility vehicle according to the invention, in which the two mutually opposite longitudinal members are designed as continuous L-shaped angle profiles. The horizontal arms of the angle profiles of the longitudinal members form the upper edges of the subframe and the vertical arms of the angle profiles form the lateral, outer edges of the subframe. In other words, the two L-shaped angle profiles are located opposite each other, and oriented in opposite directions.
In one embodiment of the invention, the connecting webs, by which the subframe is to be secured on a chassis frame of a utility vehicle, are designed as separate, flat web plates.
In a preferred embodiment, the connecting webs are formed integrally with the longitudinal members. In this case, the vertical arms of the longitudinal members extend at certain points to such a length that they make connection to the chassis frame possible.
The heights of the connecting webs are determined depending on the chassis frame on which the subframe is to be secured. The positions of the individual connecting webs within the continuous longitudinal members are likewise provided at corresponding points, and therefore can be matched with the grids of holes provided on the chassis frame.
The rigidity and strength (in particular flexural strength) of the subframe about the transverse axis of the vehicle can be influenced by a different configuration, particularly by selection of heights of the connecting webs. That is, depending on the load to be supported by the subframe, different frame heights for the subframe can be defined by selection of the heights of the connecting webs.
By defining the wall thickness of the metal sheet of the longitudinal members, the moment of inertia and also the moment of resistance of the entire longitudinal member composed of the chassis frame and the subframe can be correspondingly influenced, depending in each case on the intended use. In other words, in the case of extremely heavy loads which are to be supported by the utility vehicle with a frame structure of this type, the wall thickness of the two L-shaped longitudinal members and/or of the other component elements of the subframe is correspondingly increased.
This ensures a sufficient degree of stability and at the same time a saving of weight, since neither the continuous longitudinal members nor the individual connecting webs are designed as, for example, U-shaped or square hollow profiles.
As is customary in the case of frame structures of this type, at least one diagonal cross can be arranged between the two longitudinal members.
In a particular embodiment according to the invention, the diagonal cross provided for a subframe of this type is constructed in two parts. It is composed of an upper horizontal partial cross and a lower horizontal partial cross. The two partial crosses can be punched out in a sheet-like manner as simple cut sheet-metal parts. Vertically arranged tabs are provided at appropriate points within the partial crosses. Accordingly, the lower horizontal partial cross has upwardly pointing tabs and the upper horizontal partial cross has downwardly extending tabs at points which then correspond. The vertical tabs are bent further outwards in the one longitudinal half of the partial cross by half the thickness of the metal sheet and bent further inwards in the other longitudinal half by the thickness of the metal sheet. The diagonal cross can thus be constructed by two identical partial crosses, with one partial cross being rotated through 180° about the transverse axis of the vehicle and being screwed to the tabs which have corresponding grids of holes.
The partial crosses basically comprise two intersecting oblique struts which are connected at both longitudinal ends by cross struts. Because corresponding tabs are also provided on the cross struts, when the diagonal cross is assembled, and the upper partial cross is screwed to the lower partial cross via the individual tabs, a C-shaped angle support is formed on both cross sides and forms a corresponding degree of rigidity between the two longitudinal members.
Within the diagonal crosses, different profile heights of the entire diagonal cross can also be achieved by different lengths of the bent tabs. In this manner, the rigidity of the diagonal crosses can be influenced in a specific manner. It is thus possible in principle to configure the profile height of the diagonal crosses within the frame structure to be longer than the vertical arms of the angle profiles of the longitudinal members, or shorter or to have a corresponding length.
The rigidity of the diagonal crosses can be controlled not only by different profile heights but also by a specifically selected grid of holes in the vertical tabs.
Within the subframe structure, it is also possible to provide a plurality of diagonal crosses in order to correspondingly influence the rigidity of the subframe. Moreover, it is conceivable for different diagonal crosses to be provided over the entire length, for example a diagonal cross which comprises only a lower or an upper partial cross, and worked diagonal crosses of different heights.
In other words, the torsional rigidity and the shearing rigidity of the subframe can be determined by the number, type and individual positions of the diagonal crosses, depending on the load to be supported by said subframe.
According to the invention, the diagonal crosses are connected to the longitudinal members via U-shaped supports, which are located opposite each other in opposite directions in such a manner that their open sides point towards each other. Thus, the upper arm of the U-shaped supports can come to bear on the horizontal arms of the longitudinal members while the vertical base of the U-shaped supports is in each case connected to the vertical arms of the longitudinal members or to the connecting webs.
The diagonal crosses are connected to the U-shaped supports by, connecting the upper partial cross to the upper arm of the U-shaped support, and connecting the lower partial cross to the lower arm of the U-shaped support, on both of their sides and preferably at each corner of the diagonal crosses.
For the screw connection, the horizontal arms of the U-shaped supports protrude beyond the horizontal arms of the angle profiles of the longitudinal members. At the connecting points to the diagonal crosses, corresponding grids of holes are provided in the diagonal crosses and the horizontal arms of the U-shaped supports.
In one embodiment of the subframe according to the invention, spacers are provided between the connecting points which are each formed between the upper partial cross and the upper arm of the U-shaped support and the lower partial cross and the lower arm of the U-shaped support. These spacers are secured to the diagonal crosses via a grid of holes provided for this purpose.
According to the invention, the diagonal crosses are connected to the longitudinal members by a plurality of vertical screws which reach continuously through the partial crosses, arms of the U-shaped supports and the spacers, which and screw said elements to one another.
In principle, according to the invention, the connections between the individual components (i.e., the longitudinal members, the connecting webs, the diagonal crosses, the U-shaped supports, the spacers and, if appropriate, any crossmembers) are realized exclusively via screw connections or rivet connections.
The subframe according to the invention, with components of this type and screw connections is simple to fit and to remove. Furthermore, the invention provides a simple connection to the chassis frame via the connecting webs.
Since the auxiliary frame is constructed from simple punched and/or bent parts which merely comprise a combination of flat metal sheets and U- and L-shaped angle parts, no limit is placed on the freedom to design the subframe with regard to the intended use conditions. Furthermore, the simple parts are inexpensive to produce, since high tool costs are dispensed with.
A further advantage of the subframe according to the invention is that, depending on the use conditions, it can also be stiffened subsequently in a simple manner for example, by fitting additional diagonal crosses or by replacing the upper, L-shaped angle profiles of the longitudinal members with corresponding longitudinal members of thicker metal sheet thickness. Furthermore, the connecting webs and the angle profiles of the longitudinal members are provided with the same grids of elongated holes as the chassis frame, and the individual add-on parts are connected to a large vertical support base.
Since the material which is responsible for the weight is primarily concentrated in the continuous longitudinal members and therefore in the upper edges (or surface-layer zones) of the subframe, a subframe configured in such a manner can be produced with substantially less weight than the conventional type known from the prior art.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.